Design and performance prediction of pyrolysis furnaces by flux methods and by the zone method

Abstract

The major problem of high temperature, high pressure, low residence time operations is the prediction of the heat flux profiles on the pyrolysis furnace tube walls, where the tube skin temperature becomes the limiting factor. Solution of this problem by numerical methods requires high space resolution of the volume and walls of the furnace. This results in large sets of non-linear energy balance equations, to be solved simultaneously with the radiative transport equation. The zone method and the flux methods provide two different treatments of the radiative transport equation; they lead to sparse and tridiagonal matrices, respectively. The theoretical principles of each approach are briefly outlined, the accuracy and computational load discussed, and the application to the case of a typical pyrolysis furnace shown. The effects of space resolution and of improving the model of radiative properties of the combustion products are also examined.